If the magnetic energy within the cloud of superhot gas had interacted with the Earth's magnetic field it would have sparked spectacular aurora at polar latitudes.

But more worryingly it could also induce power blackouts, block radio communications and trigger phantom commands capable of sending satellites spinning out of their proper orbits.

Cellular phones, global positioning signals and space-walking astronauts were all at risk.

Hit or miss?

"When the coronal mass ejection was observed we were not sure whether the mass ejection was moving toward the Earth or directly away from the Earth" said Paal Brekke, SOHO Deputy Project Scientist.

Astronomers were particularly concerned that the event was followed by an increase in the flux of sub-atomic particles from the Sun.

So the scientists quickly downloaded Internet images of the Sun taken by observatories in the USA, Austria, Australia, and Japan. They then compared images the taken before and after the event.

"Because the data are so distributed and so accessible we were able to identify and track this event," said one astronomer. "Even just a few years ago, this kind of instant international collaboration would have been impossible."

Fortunately, it was soon established that the CME was headed directly away from the Earth - this time.

Preliminary analysis by Dr Simon Plunkett, of the Naval Research Laboratory in the United States, shows that if the CME were travelling towards the Earth, it would have arrived in just two and a half days.

The other Y2K problem

Solar activity waxes and wanes in an 11-year cycle, which is expected to peak sometime early next year.

Astronomers point out that the solar menace comes at the same time as computers around the world could struggle to cope with problems caused by the Millennium or Year 2000 (Y2K) bug.

Some solar physicists have called the effects from the Sun "the other Y2K problem".

"The SOHO satellite will play a key role in early detection of solar storms, which is important for issuing warnings," added Dr Brekke.